(a) Field of the Invention
The present invention relates to a method and apparatus for eliminating a display defect in a liquid crystal display device, and in particular, to a method and apparatus for removing a bubble between a substrate and a polarizer.
(b) Description of Related Art
Generally, a liquid crystal display device includes a liquid crystal panel. The liquid crystal panel includes a thin film transistor (TFT) array substrate, a color filter substrate, and a liquid crystal layer disposed between the TFT array substrate and the cooler filter substrate. Typically, the TFT array substrate and the cooler filter substrate each include an attached polarizer. Since TFTs are non-emissive elements, a backlight unit for providing light to the TFT array substrate is usually located at a rear side of the liquid crystal panel. Transmittance of light emitted from the backlight unit and passing through the liquid crystal panel is controlled by altering orientations of liquid crystal molecules in the liquid crystal layer.
In addition, the liquid crystal display device includes a controller, a data driver, and a gate driver, so as to drive pixels of the liquid crystal panel. The data driver and the gate driver supply a voltage to data lines and gate lines, respectively, responsive to signals from the controller.
As stated above, polarizers are often attached to an exterior surface of both the TFT array substrate and the cooler filter substrate. However, a bubble may be formed between the exterior surface of either the TFT array substrate or the color filter substrate and a corresponding one of the polarizers. Such a bubble deteriorates adhesion between either the TFT array substrate or the color filter substrate and the corresponding one of the polarizers, thereby deteriorating display quality.
FIG. 1 is a perspective view showing a bubble removing apparatus according to the prior art.
As shown in FIG. 1, a bubble removing apparatus 100 according to the prior art includes a case 110 forming a chamber 130 and a door 120 that may be opened and closed for allowing entry into the case 110. The chamber 130 accommodates a liquid crystal panel 140. In addition, the bubble removing apparatus 100 according to the prior art includes a pump (not shown) for supplying gas to provide a predetermined pressure in the chamber 130, and a heater (not shown) for supplying heat to provide a predetermined temperature in the chamber 130.
A method for removing a bubble using the bubble removing apparatus 100 according to the prior art will hereinafter be described.
The door 120 is drawn to open the case 110 and expose the chamber 130. Thereafter, a plurality of liquid crystal panels 140 are loaded in the chamber 130 at one time. During loading of the liquid crystal panels, a temperature and pressure of the chamber 130 are room temperature and atmospheric pressure, respectively. After the liquid crystal panels 140 are loaded in the chamber 130, the door 120 is closed such that the chamber 130 becomes airtight.
Thereafter, the temperature and the pressure of the chamber 130 are increased to predetermined levels. The increased temperature and pressure cause a bubble formed between an external surface of a substrate and a polarizer to move to an edge of the substrate of each of the liquid crystal panels 140. At a sufficient temperature and pressure, the bubble is forced off the edge of the substrate and is thus removed. After the bubble is removed, the temperature and pressure of the chamber 130 are decreased back to room temperature and atmospheric pressure. Thereafter, the door 120 is opened to expose the chamber 130, and the liquid crystal panels 140 are extracted from the chamber 130.
FIG. 2 is a graph showing changes of temperature and pressure in the chamber 130 with respect to time, according to such a conventional bubble removing apparatus.
Section “I” in FIG. 2 shows a first step in which the temperature and pressure of the chamber 130 are increased from room temperature and atmospheric pressure to the predetermined temperature and pressure, respectively. The first step consumes about 8 minutes. Section “II” in FIG. 2 shows a second step in which the temperature and pressure of the chamber 130 are maintained at the predetermined temperature and pressure, respectively. The second step consumes about 15 minutes. Section “III” in FIG. 2 shows a third step in which the temperature and pressure of the chamber 130 are respectively decreased from the predetermined temperature and pressure to room temperature and atmospheric pressure. The third step consumes about 7 minutes.
A conventional bubble removing method as described above has several drawbacks including those described below.
First, since the liquid crystal panels 140 are placed into and extracted from the chamber 130 at room temperature and atmospheric pressure, excessive time is consumed for increasing (or decreasing) the temperature and pressure of the chamber 130 to the predetermined temperature and pressure (or to room temperature and atmospheric pressure).
Second, the liquid crystal panels 140 are loaded into and extracted from the chamber 130 in discrete batches. Accordingly, a separate process line is required, such as, for example, a transferring process line in which the batch of the liquid crystal panels 140 is transferred by a transferring device separate from a conveyer line. Operation of the separate process line means the liquid crystal panels 140 are subject to additional handling, which must be done with great care in order to prevent damage to the liquid crystal panels 140. Such additional handling adds to production time, and particularly if a size of a liquid crystal panel 140 is large, more caution is required to prevent the liquid crystal panel 140 from being interfered with by surrounding devices.
Third, a production process involving the conventional bubble removing method is not completed within one assembly line, and accordingly productivity is deteriorated.